This summer should be big for Hollywood, but many favorites won't top ticket sales by their predecessors. Are film fans fed up with sequels?

NEW YORK (CNNMoney.com) -- This summer's big movies have gotten off to big starts at the box office but have fizzled fast, leading some industry analysts to wonder if filmgoers are feeling burned out by all the sequels at the multiplex.

Sony's (Charts) "Spider-Man 3" kicked off the summer movie season with a record-breaking $151.1 million during the first weekend of May, according to figures from movie industry research site Box Office Mojo.

Why the long face, Jack? It might be because "Pirates of the Caribbean: At World's End" isn't going to come close to matching the box office gold of last year's "Dead Man's Chest."

Romantic comedy "Knocked Up" is a rarity this summer. It's not a sequel. Good reviews and repeat business have the movie on track to gross $100 million in the United States.

"Transformers" may be based on the popular toys from Hasbro. And there was a cartoon movie in the 1980s. But this isn't a true sequel, and that has raised hopes that the movie can stand out and deliver big box office in the latter half of the summer.

But as of June 18, the movie's total U.S. box office gross was $330.3 million. Since the movie has already been out for eight weeks and grossed only $2.5 million last weekend, it will probably be difficult to match "Spider-Man 2"'s domestic take of $373.6 million in 2004, let alone the $403.4 million that the first film grossed in 2002.

It's a similar story for "Shrek the Third," produced by DreamWorks Animation (Charts). The movie had a record opening for an animated film, grossing $121.6 million in its first weekend.

And while the film's $298.4 million in total U.S. box office so far is higher than the original's $267.7 million from 2001, it's extremely doubtful the film will top "Shrek 2"'s $441.2 million take from 2004.

Then there's "Pirates of the Caribbean: At World's End," a movie that many analysts predicted would be this summer's box office champ. It sold an impressive but not record-breaking $114.7 million's worth of tickets in its first weekend.

But the Disney (Charts, Fortune 500) film has gone on to gross $275.6 million overall. Last week, the film's fourth week in release, generated only $12.4 million at the box office. So "At World's End" may struggle to top the $305.4 million that the first film grossed in 2003 and will come in well below the $423.3 million that "Dead Man's Chest" took in last summer.

"There was definitely a case of sequel-itis this summer," said Jeff Bock, a box office analyst at Exhibitor Relations, a Los Angeles industry research firm. "With sequels, there are definitely some audiences that rush to these films in the first couple of weeks but then the box office erodes much quicker."

"At World's End," suffered from another problem. Disney may have miscalculated interest in the franchise when it decided to film the second and third movies simultaneously and release them just 10 months apart.

Typically, studios tend to release sequels to big hits two or three years after the last film in order to build up enough time to create pent-up demand. So while enough time had lapsed to get fans interested in what was happening to Spidey and Shrek, the same may not have been true for Jack Sparrow.

"There may not have been enough time to build up true anticipation. If your favorite concert act comes to town every year, are going to shell out big money on StubHub every summer to get seats? Probably not," said Michael Coristine, lead media analyst with BrandIntel, a market research firm that tracks consumer opinion on blogs, message boards and other Internet sites. "If you're going to put out a sequel, you need to give people time to get hyped up."

And these are the big hits. Other summer sequels, such as "Ocean's 13," "Hostel 2" and "28 Weeks Later," have underperformed compared to their predecessors.

The most recent big sequel, "Fantastic Four: Rise of the Silver Surfer," which hit theaters on June 15, did slightly better in its opening weekend than the original movie. But it remains to be seen if the film, released by News Corp.'s (Charts, Fortune 500) Fox studio, can hold up at the box office or if, like "Spider-Man," "Shrek" and "Pirates," it will suffer a precipitous drop in its second week and beyond.

"The big sequels are sprinters more than marathoners. If you are an established fan of the first two movies, it's almost an obligation to see the third. But then there's the burnout," Coristine said.

This many not be a good sign for upcoming sequels such as Fox's "Live Free or Die Hard", the fourth in the Bruce Willis action series but the first since 1995, as well as Warner Bros.' "Harry Potter and the Order of the Phoenix," the fifth movie based on the series of books about the boy wizard. Warner. Bros. is owned by Time Warner (Charts, Fortune 500), which also owns CNNMoney.com.

Instead, "original" movies such as "Ratatouille," the latest animated film from Disney and Pixar, due out on June 29; "Transformers," which is being released by Viacom's (Charts, Fortune 500) Paramount and DreamWorks SKG studios on July 3; and "I Now Pronounce You Chuck and Larry," a comedy from GE's (Charts, Fortune 500) Universal Studios starring Adam Sandler that will hit theaters on July 20, could stand a better chance of garnering repeat business than the sequels.

"'Transformers' has an edge because it's not a sequel. That will be the film to catch for the second half of the summer. As for 'Ratatouille,' Pixar has never had a misstep. And this film is no less compelling than the others. It will gross over $200 million," said Exhibitor Relations' Bock. The novelty factor has appeared to help "Knocked Up," the comedy about getting pregnant after a one-night stand from the writer and director of the 2005 sleeper hit "The 40 Year-Old Virgin." Critics adored the movie, and it definitely stood out amidst all the sequel noise.

"Knocked Up" debuted on June 1 and held its own against the second weekend of "Pirates" with an impressive $30.7 million in its opening weekend. What's more, "Knocked Up" racked up $19.6 million and $14 million in its next two weekends, a much lower drop in box office than this summer's big sequels have experienced.

The movie has taken in $92.2 million so far, which means it stands a good chance of matching or topping the $109.4 million that "The 40 Year-Old Virgin" made at the box office.

"'Knocked Up' did decent business in the second week since some people waited to hear how good it was," Coristine said. "And I haven't seen universally good reviews for a movie this summer other than 'Knocked Up'. Plus, every week there's something coming out that's a sequel and audiences are always up for something new."

Interestingly though, sequel fatigue is only a U.S. phenomenon. According to Box Office Mojo, "Spider-Man 3" has already topped the global box office figures set by its two predecessors.

"Spider-Man 3" has grossed $874.2 million, surpassing the $821.7 million worldwide box office take of "Spider-Man." Meanwhile, "At World's End," despite not living up to some lofty expectations in the United States, has grossed $822.6 million worldwide. Bock thinks the third "Pirates" movie has a chance to come close to the $1.06 billion global box office take that "Dead Man's Chest" grossed last year.

"Domestically, some of these sequels may be disappointing but worldwide it's quite eye-opening for the studios. The big 'tent pole' movies are not just for the U.S. market anymore," he said.

The reporter of this story owns shares of Time Warner through his company's 401(k) plan.